US2990457A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tandem echo suppressor circuits
Assignee: AT&T Inc
•
Filing: 1958-02-04
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Granted: 1961-06-27
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Expires: 1978-02-04
Abstract
No abstract record available.
Inventors
- 👤 Arthur D Hall
- 👤 Zarouni Alfred
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 02:46
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1964-06-26 | 1964-12-26 | 1965-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1968-06-26 | 1968-12-26 | 1969-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1972-06-26 | 1972-12-26 | 1973-06-27 | $7700.00 | Window Closed / Lapsed |